The present invention relates to a sheet feeding device used in a data reading apparatus, a printing apparatus or the like to feed plural sheets of paper one by one to a processing section.
A roller type sheet feeding device used in a printer, a facsimile machine, a copying machine or the like has been generally known as a sheet feeding device.
In most cases, the roller type sheet feeding device of this kind has a cylindrical sheet feeding roller disposed at the downstream side in a sheet feeding direction, so that a sheet of paper is fed as the sheet feeding roller pulls in the sheet of paper from the vicinity of the leading end thereof.
This is because sheet feeding operations become more stable regardless of the paper rigidity by feeding sheets of paper while holding the vicinity of their leading ends. In addition, for a sheet feeding device of a type in which a separating pad is disposed downstream of a sheet feeding roller to separate sheets of paper one by one by friction produced when the leading end of a sheet of paper slides on the separating pad, it is advantageous to dispose the separating pad and the sheet feeding roller in close relation to each other in increasing the performance capability of separating plural sheets.
However, when the sheet feeding roller is disposed at the downstream side of the sheet feeding device in the sheet feeding direction, in a case where the leading ends of sheets of paper are not aligned neatly, there may be a sheet of paper whose leading end does not reach the position at which the leading end is supposed to come into contact with the sheet feeding roller. In such a case, the sheet feeding roller fails to pull in the leading end of the sheet of paper, and the sheet feeding device may become unable to feed the sheet of paper.
Normally, a counter measure to align the leading ends of sheets of paper is taken in a typical sheet feeding device, and the counter measure is broadly divided into two methods as follows.
One is a method often adapted in a laser printer, a copying machine and the like, and it is a method for positioning sheets of paper precisely on the left, right, top, and bottom by placing the sheets of paper horizontally within a sheet feeding cassette (cf., Japanese Patent Publication No. 8-277044A, for example).
The other is a method often adapted in an ink jet printer and the like, and it is a method for letting the leading ends of sheets of paper fall down to the pad portion at the lower end by gravity by setting the sheets of paper in a downward orientation (placing the sheets of paper vertically) (cf., Japanese Patent Publication No. 62-153033A, for example).
A sheet feeding cassette is necessary, however, with the method for positioning sheets of paper on the left, right, top, and bottom precisely by placing the sheets of paper horizontally, and this method makes it difficult to reduce the sheet feeding device in size.
The sheet feeding device can be reduced in size with the method for letting the leading ends of sheets of paper fall down to the pad at the lower end by gravity by setting the sheets of paper in a downward orientation. The installation posture is limited, however, because sheets of paper cannot be fed unless they are set in the vertical direction.